Create 0451-sort-characters-by-frequency.java

Author: sujal-goswami

java/0451-sort-characters-by-frequency.java

@@ -0,0 +1,31 @@
+class Solution {
+    public String frequencySort(String s) {
+        Map<Character, Integer> map = new HashMap<>();
+        for(char c: s.toCharArray())
+            map.put(c, map.getOrDefault(c, 0) + 1);
+
+        PriorityQueue<pair> q = new PriorityQueue<>((a, b) -> b.f - a.f);
+        for(char c: map.keySet())
+            q.add(new pair(c, map.get(c)));
+        
+        StringBuilder res = new StringBuilder();
+        while(!q.isEmpty()){
+            pair r = q.poll();
+            int f = r.f;
+            while(f > 0){
+                res.append(r.c);
+                f--;
+            }
+        }   
+        return res.toString();    
+    }
+}
+class pair{
+    char c;
+    int f;
+    
+    public pair(char c, int f){
+        this.c = c;
+        this.f = f;
+    }
+}